Investigating the effectiveness of antacids
Aseel Samaro
Introduction
 Heartburn indigestion is caused by acid from the stomach irritating
the upper digestive tract.
 For those who suffer regularly, treatments are available to neutralise
this acid.
 But are some remedies more effective than others
The need of antacids
 The human stomach contains strong hydrochloric acid, with a pH of
approximately 1.
 The role of this acid is to enable the digestion of proteins in the stomach and also
to prevent many bacteria from surviving in the stomach.
 Sometimes the muscle leading from the oesophagus to the stomach can open
and the acid moves up along the digestive tract.
 A burning sensation is then felt in the chest and throat as the acid irritates the
lining of the oesophagus.
This is called indigestion or heartburn.
Describe what type of acid is found in the stomach and comment on
its strength.
Describe two reasons why we have acid in the stomach.
Explain what heartburn is and what causes it.
Describe what type of acid is found in the stomach and comment on its strength.
hydrochloric acid; strong (pH 1)
Describe two reasons why we have acid in the stomach.
digestion of proteins; prevention of the survival of some bacteria
Explain what heartburn is and what causes it.
a burning sensation in the chest and throat; caused by stomach acid moving up the
oesophagus
Alkalis in action
 One of the main treatments for heartburn involves neutralising the acid from the stomach.
 Medicines that do this are called antacids.
 Antacid remedies contain substances, such as:
 calcium carbonate
 aluminium hydroxide
 sodium hydrogencarbonate (baking soda).
 These substances neutralise acids, as alkalis do. However, they do not dissolve in water, as alkalis
do, and are known as bases.
 Bases react with acids in a neutralisation reaction: acid + base → salt + water
 Because the both salt and water are neutral, antacids reduce the acidity of the stomach acid.
List some of the main ingredients found in heartburn remedies.
Explain how antacids reduce the acidity of stomach acid.
Suggest the effect of antacid remedies on the pH of stomach acid.
List some of the main ingredients found in heartburn remedies.
Calcium carbonate; magnesium hydroxide
Explain how antacids reduce the acidity of stomach acid.
An alkali (or base) neutralises the stomach acid; making the solution less
acidic
Suggest the effect of antacid remedies on the pH of stomach acid.
Increase the pH
Which remedy?
 A group of students wanted to compare
the effectiveness of different commercial
antacid remedies.
 They first added universal indicator to a
beaker of hydrochloric acid to check that it
was a strong acid (pH 1).
 They added the recommended dose of
each antacid to the acid. The students
observed any colour change and noted
how long any change took.
Explain why it was important to start with acid of pH 1.
Describe which remedy is the most effective. Explain your answer as fully
as possible.
Another student suggests that the experiment is repeated using crushed
‘Acid-ban’ tablets, rather than whole tablets. Suggest how this will affect
the time taken to change the pH.
Explain why it was important to start with acid of pH 1.
stomach acid is approximately pH 1–2
Describe which remedy is the most effective. Explain your answer as fully as
possible.
‘Acid-ease’ liquid; it changes the pH from 1 to 6; takes only 3 minutes
Another student suggests that the experiment is repeated using crushed ‘Acidban’ tablets, rather than whole tablets. Suggest how this will affect the time
taken to change the pH.
The time may decrease; because of increased surface area of ‘Acid-ban’ tablets
Did you know?
 Even before the chemistry was understood, acid-neutralising
remedies were recommended for heartburn.
 One remedy was to chew limestone rock.
 We now know that limestone contains the base calcium carbonate